151 
and intercrossing muscle fibres. The first diaphragm is 
perforated by some of the retractors of the proboscis, and 
it bears two backwardly projecting pear-shaped or finger- 
shaped out-growths which lie to the sides of, and ventral 
to, the esophagus (fig. 23). These are not cesophageal 
glands. They open anteriorly into the ceelomic space in 
front of the first septum. Their walls are muscular and 
very vascular and they contract at frequent intervals 
during life. Their function is unknown, they may pos- 
sibly be of use in aiding the eversion of the proboscis. 
The occurrence of rudimentary septa accompanying 
some of the afferent and efferent vessels of the nephridia 
and gills, and the probable function of the two strands 
(septa) attached to the efferent vessel of the fourth 
nephridium have been described above. 
The caudal septa are incomplete ventrally and ventro- 
laterally, z.e., above and at the sides of the nerve cord. 
Hach is composed of two thin layers of coelomic epithe- 
hum, forming the anterior and posterior faces between 
which is a small quantity of connective tissue and muscle 
fibres. These septa are not fenestrated like the three 
anterior diaphragms. ‘There are in the tail, in addition 
to these septa, dorsal and ventral mesenteries, by means 
of which the intestine is attached above and below to the 
body wall and in which lie the dorsal and ventral blood- 
vessels. Owing to their small size these mesenteries are 
with difficulty seen in dissections, but they are readily 
distinguished in transverse sections of the tail. 
Ca@tom anp Ca@tomic FLuIp. 
The ceelom, which is lined by a layer of flattened 
cells, is spacious and continuous from end to end of the 
animal. It is partly sub-divided by septa in the anterior 
